Helically wound, rigid, non-metallic tubular container wall materials having a foil interior surface and adapted with closure members secured to either end are well-known in the art. The use of these non-metallic wound containers in lieu of essentially metallic cans and other packaging forms offers a considerable savings in material costs.
Containers of this type have generally been made by successively winding webs of metallic foil or foil laminate and then rigidity and structure imparting material helically onto a mandrel to form a layered tubular wall member. A laminate such as a metallic foil-paper has most often been used as the inner, liner material rather than the heavy gauge unsupported foil web which would otherwise be required.
Containers of the foregoing type, however, often fail to withstand attack from corrosive contents in the absence of a protective coating applied to the innermost foil or foil-laminate surface. Additionally, abrasive contents have been known to destroy laminated coating on the inner metallic foil surface so as to expose the metal and render such laminates ineffective.
A further drawback in the use of the prior art metallic foil and foil-laminate liners attend the production of these tubular wall materials in the successive, helically winding onto a mandrel. Because the wound tube must rotate relative to, and be slidingly removable from, the mandrel, it is essential that the mandrel-contacting ply of the wall material be of low frictional resistance.
In the prior art, however, the metallic foil and metallic foil laminates have not provided the requisite low coefficient of friction on the mandrel. Accordingly, it has been necessary to apply a lubricant to the mandrel itself, or to the mandrel-contacting layer, before and continuously throughout the winding operation. Such lubrication has the disadvantage of requiring careful monitoring throughout the tube forming operation. Further, and particularly in instances wherein the container is intended for use in the canning of an edible material, such lubricant often constitutes an impurity which could cause contamination unless subsequently removed or otherwise rendered harmless.
In the prior art, the forming of a continuous barrier ply of the liner has also proven a problem. Often such ply has proven weak or discontinuous at the seam formed during winding or, in alternative construction, reinforced seams have interfered with proper seating of the end closure means of the container.
It is therefore an object of the present invention to overcome the foregoing drawbcks. Additionally, the present invention provides such other advantages as are hereinafter described.